Plant Hormones & Movement

Hormones What do you need to know? 1. Where are they produced? 2. How are they transported? 3.How does the plant respond? 4.Commercial uses  Start with the definition – a chemical that is produced in one part of the plant, then transported to another where it causes a physiological change.

Auxins 1.Apical meristems 2.Active transport 3.Weakens fibers to allow growth 4.Promotes rooting, inhibits branching, delays fruit formation & leaf/fruit drop

Gibberellins 1.Location unknown 2.Vascular issue 3.Stimulate cell division & elongation 4.Increased production of grapes, more malt production in barley (more beer!), increased production of sugar in sugar cane. Breaks dormancy in seeds

Application of gibberellins

Cytokinins 1.Roots 2.Xylem 3.Stimulates mitosis & cell division when combined with auxins 4.Prolong the storage life of green vegetables (asparagus, broccoli & celery)

Ethylene Gas 1.Produced by ripening or dying tissues 2.Diffusion 3.Promotes ripening in fruit 4.Makes mechanical harvesting of fruits and veggies easier

Plant responses Tropic response  Slow movement caused by growth - irreversible  Positive tropism – growth is towards stimulus  Negative tropism – growth is away from stimulus  Ex. Phototropism & gravitropism Nastic movement  Rapid movement caused by change in water pressure - reversible  Response is always the same – not towards or away from stimulus  Ex. – Venus flytrap & Mimosa plants